pct.adoc

   1 ifdef::manvolnum[]
   2 PVE({manvolnum})
   3 ================
   4 include::attributes.txt[]
   5
   6 NAME
   7 ----
   8
   9 pct - Tool to manage Linux Containers (LXC) on Proxmox VE
  10
  11
  12 SYNOPSYS
  13 --------
  14
  15 include::pct.1-synopsis.adoc[]
  16
  17 DESCRIPTION
  18 -----------
  19 endif::manvolnum[]
  20
  21 ifndef::manvolnum[]
  22 Proxmox Container Toolkit
  23 =========================
  24 include::attributes.txt[]
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  26
  27
  28 Containers are a lightweight alternative to fully virtualized
  29 VMs. Instead of emulating a complete Operating System (OS), containers
  30 simply use the OS of the host they run on. This implies that all
  31 containers use the same kernel, and that they can access resources
  32 from the host directly.
  33
  34 This is great because containers do not waste CPU power nor memory due
  35 to kernel emulation. Container run-time costs are close to zero and
  36 usually negligible. But there are also some drawbacks you need to
  37 consider:
  38
  39 * You can only run Linux based OS inside containers, i.e. it is not
  40   possible to run Free BSD or MS Windows inside.
  41
  42 * For security reasons, access to host resources need to be
  43   restricted. This is done with AppArmor, SecComp filters and other
  44   kernel feature. Be prepared that some syscalls are not allowed
  45   inside containers.
  46
  47 {pve} uses https://linuxcontainers.org/[LXC] as underlying container
  48 technology. We consider LXC as low-level library, which provides
  49 countless options. It would be to difficult to use those tools
  50 directly. Instead, we provide a small wrapper called `pct`, the
  51 "Proxmox Container Toolkit".
  52
  53 The toolkit it tightly coupled with {pve}. That means that it is aware
  54 of the cluster setup, and it can use the same network and storage
  55 resources as fully virtualized VMs. You can even use the {pve}
  56 firewall, or manage containers using the HA framework.
  57
  58 Our primary goal is to offer an environment as one would get from a
  59 VM, but without the additional overhead. We call this "System
  60 Containers".
  61
  62 NOTE: If you want to run micro-containers (with docker, rct, ...), it
  63 is best to run them inside a VM.
  64
  65
  66 Security Considerations
  67 -----------------------
  68
  69 Containers use the same kernel as the host, so there is a big attack
  70 surface for malicious users. You should consider this fact if you
  71 provide containers to totally untrusted people. In general, fully
  72 virtualized VM provides better isolation.
  73
  74 The good news is that LXC uses many kernel security features like
  75 AppArmor, CGroups and PID and user namespaces, which makes containers
  76 usage quite secure. We distinguish two types of containers:
  77
  78 Privileged containers
  79 ~~~~~~~~~~~~~~~~~~~~~
  80
  81 Security is done by dropping capabilities, using mandatory access
  82 control (AppArmor), SecComp filters and namespaces. The LXC team
  83 considers this kind of container as unsafe, and they will not consider
  84 new container escape exploits to be security issues worthy of a CVE
  85 and quick fix. So you should use this kind of containers only inside a
  86 trusted environment, or when no untrusted task is running as root in
  87 the container.
  88
  89 Unprivileged containers
  90 ~~~~~~~~~~~~~~~~~~~~~~~
  91
  92 This kind of containers use a new kernel feature, called user
  93 namespaces. The root uid 0 inside the container is mapped to an
  94 unprivileged user outside the container. This means that most security
  95 issues (container escape, resource abuse, ...) in those containers
  96 will affect a random unprivileged user, and so would be a generic
  97 kernel security bug rather than a LXC issue. LXC people think
  98 unprivileged containers are safe by design.
  99
 100 Container Storage
 101 -----------------
 102
 103 Traditional containers use a very simple storage model, only allowing
 104 a single mount point, the root file system. This was further
 105 restricted to specific file system types like 'ext4' and 'nfs'.
 106 Additional mounts are often done by user provided scripts. This turend
 107 out to be complex and error prone, so we trie to avoid that now.
 108
 109 Our new LXC based container model is more flexible regarding
 110 storage. First, you can have more than a single mount point. This
 111 allows you to choose a suitable storage for each application. For
 112 example, you can use a relatively slow (and thus cheap) storage for
 113 the container root file system. Then you can use a second mount point
 114 to mount a very fast, distributed storage for your database
 115 application.
 116
 117 The second big improvement is that you can use any storage type
 118 supported by the {pve} storage library. That means that you can store
 119 your containers on local 'lvmthin' or 'zfs', shared 'iSCSI' storage,
 120 or even on distributed storage systems like 'ceph'. And it enables us
 121 to use advanced storage features like snapshots and clones. 'vzdump'
 122 can also use the snapshots feature to provide consistent container
 123 backups.
 124
 125 Last but not least, you can also mount local devices directly, or
 126 mount local directories using bind mounts. That way you can access
 127 local storage inside containers with zero overhead. Such bind mounts
 128 also provides an easy way to share data between different containers.
 129
 130
 131 Managing Containers with 'pct'
 132 ------------------------------
 133
 134 'pct' is a tool to manages Linux Containers (LXC). You can create and
 135 destroy containers, and control execution
 136 (start/stop/suspend/resume). Besides that, you can use pct to set
 137 parameters in the associated config file, like network configuration
 138 or memory.
 139
 140 CLI Usage Examples
 141 ------------------
 142
 143 Create a container based on a Debian template (provided you downloaded
 144 the template via the webgui before)
 145
 146  pct create 100 /var/lib/vz/template/cache/debian-8.0-standard_8.0-1_amd64.tar.gz
 147
 148 Start container 100
 149
 150  pct start 100
 151
 152 Start a login session via getty
 153
 154  pct console 100
 155
 156 Enter the LXC namespace and run a shell as root user
 157
 158  pct enter 100
 159
 160 Display the configuration
 161
 162  pct config 100
 163
 164 Add a network interface called eth0, bridged to the host bridge vmbr0,
 165 set the address and gateway, while it's running
 166
 167  pct set 100 -net0 name=eth0,bridge=vmbr0,ip=192.168.15.147/24,gw=192.168.15.1
 168
 169 Reduce the memory of the container to 512MB
 170
 171  pct set -memory 512 100
 172
 173 Files
 174 ------
 175
 176 '/etc/pve/lxc/<vmid>.conf'::
 177
 178 Configuration file for the container <vmid>
 179
 180
 181 Container Advantages
 182 --------------------
 183
 184 - Simple, and fully integrated into {pve}. Setup looks similar to a normal
 185   VM setup.
 186
 187   * Storage (ZFS, LVM, NFS, Ceph, ...)
 188
 189   * Network
 190
 191   * Authentification
 192
 193   * Cluster
 194
 195 - Fast: minimal overhead, as fast as bare metal
 196
 197 - High density (perfect for idle workloads)
 198
 199 - REST API
 200
 201 - Direct hardware access
 202
 203
 204 Technology Overview
 205 -------------------
 206
 207 - Integrated into {pve} graphical user interface (GUI)
 208
 209 - LXC (https://linuxcontainers.org/)
 210
 211 - cgmanager for cgroup management
 212
 213 - lxcfs to provive containerized /proc file system
 214
 215 - apparmor
 216
 217 - CRIU: for live migration (planned)
 218
 219 - We use latest available kernels (4.2.X)
 220
 221 - image based deployment (templates)
 222
 223 - Container setup from host (Network, DNS, Storage, ...)
 224
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